1. Field of the Invention
This invention pertains to a stop for use with an extensible hydraulic cylinder. Particularly, the invention is a retractable boom stop for use with a boom arm lift cylinder of a skid steer vehicle.
2. Description of the Prior Art
Boom stops for the lift cylinders on an off road vehicle are in widespread use. A typical stop member for a lift cylinder is disclosed in the Luedtke et al. U.S. Pat. No. 3,982,648. This stop member is pivotally attached at one end to the boom arm of the vehicle by a pivotable link assembly. To retain the lift cylinder in an extended state the opposite end of the stop member is engaged with a forward end of the lift cylinder body. Once engaged any retraction of the lift cylinder causes the stop member to be wedged between the pivotable link assembly and forward end of the lift cylinder body. To disengage the stop member requires that the lift cylinder be extended and the stop member be manually moved to an inoperative position.
The Albright et al. U.S. Pat. No. 4,043,253 discloses a boom stop for the lift cylinder of an off road vehicle that is pivotally mounted at one end to the boom arm pivot mount for the lift cylinder extensible rod. The boom stop includes a body portion that rests on the lift cylinder body when the lift cylinder is in a retracted state. As the lift cylinder is extended the boom stop rides along the body of the lift cylinder until the opposite end of the boom stop engages the forward end of the cylinder body. Retracting the lift cylinder causes the boom stop to be wedged between the forward end of the cylinder body and the pivot mount for the extensible rod. The boom stop includes a pivotable toggle having a ramped surface that disengages the boom stop from the lift cylinder. Extension followed by retraction of the lift cylinder rotates the toggle to allow the ramped surface to ride over the outer end of the lift cylinder body and thereby disengage the boom stop. This boom stop cannot be moved to an inoperative position adjacent the boom arm. Therefore, it can interfere with the normal operation of the boom arm since the boom stop operates automatically when the lift cylinder is extended.
It is evident that there is a continuing need for improved boom stops for lift arms. Specifically, a retractable boom stop is needed that automatically disengages from its operative state and does not interfere with the normal operation of the boom arms of the off road vehicle.